Corrugated microwave horns and the like

ABSTRACT

A corrugated microwave horn or the like is constructed by forming a plurality of thin, parallel, annular plates of conductive metal with a multiplicity of integral tabs spaced around the periphery of each plate. A thin flat sheet of flexible conductive metal is formed with a multiplicity of spaced parallel slots arranged in a multiplicity of longitudinal columns and transverse rows. One of the tabs on each of the annular plates is fitted through the slots in one of the longitudinal columns, and a wire is inserted through apertures in the tabs to lock the slotted sheet to the annular plates. The slotted sheet is then rolled around the peripheries of the plates to fit successive tabs through the successive longitudinal columns of slots, and additional wires are inserted through the apertures in successive tabs to lock the sheet to successive portions of the peripheries of the plates. To provide a continuous electrical connection between the rolled sheet and the peripheries of the annular plates, the entire assembly may be soldered together by simply coating the outer surface of the assembly with a paste solder and then heating it. The tabs may be formed on the inner peripheries rather than the outer peripheries of the plate members, and the slotted sheet formed of resilient metal so that it is biased against the inner peripheries of the plate members without the use of any wires or other longitudinal locking members.

United States Patent [1 Phillips 11] 3,914,861 Oct. 28, 1975 CORRUGATEDMICROWAVE HORNS AND THE LIKE [75] Inventor: James P. Phillips, Lockport,Ill.

[73] Assignee: Andrew Corporation, Orland Park,

Ill.

[22] Filed: Sept. 16, I974 [21] Appl. No.: 506,168

[52] US. Cl. 29/600; 29/l57.3 A; 29/471.3; 29/502; 29/526; 165/182;333/95 R [51] Int. Cl. 343 786; H01? 11/00 [58] Field of Search 29/600,157.3 A,'428, 450, 29/457, 460, 470.7, 471.3, 502, 526, 202 R,

Primary ExaminerC. W. Lanham Assistant Examiner.loseph A. WalkowskiAttorney, Agent, or F irmWolfe, Hubbard, Leydig, Voit & Osann, Ltd.

lull/ll [5 7] ABSTRACT A corrugated microwave horn or the like isconstructed by forming a plurality of thin, parallel, annular plates ofconductive metal with a multiplicity of integral tabs spaced around theperiphery of each plate. A thin flat sheet of flexible conductive metalis formed with a multiplicity of spaced parallel slots arranged in amultiplicity of longitudinal columns and transverse rows. One of thetabs on each of the annular plates is fitted through the slots in one ofthe longitudinal columns, and a wire is inserted through apertures inthe tabs to lock the slotted sheet to the annular plates. The slottedsheet is then rolled around the peripheries of the plates to fitsuccessive tabs through the successive longitudinal columns of slots,and additional wires are inserted through the apertures in successivetabs to lock the sheet to successive portions of the peripheries of theplates. To provide a continuous electrical connection between the rolledsheet and the peripheries of the annular plates, the entire assembly maybe soldered together by simply coating the outer surface of the assemblywith a paste solder and then heating it. The tabs may be formed on theinner peripheries rather than the outer peripheries of the platemembers, and the slotted sheet formed of resilient metal so that it isbiased against the inner peripheries of the plate members without theuse of any wires or other longitudinal locking members.

I 9 Claims, 6 Drawing Figures U.S. Patem 0m. 28, 1975 Sheet 1 of 2 US.Patent Oct. 28, 1975 Sheet2 0f2 3,914,861

CORRUGATED MICROWAVE HORNS AND THE LIKE DESCRIPTION OF THE INVENTIONThis invention relates to corrugated microwave horns and the like and,more particularly, to a new construction for such corrugated horns andthe like which greatly simplifies their manufacture.

Corrugated horns have been known and used as feed horns for microwaveantennas for several years. These horns are usually corrugated" only onthe inside surface, i.e., they have a number of transverse ribs on theinside surface of the horn, these ribs being spaced apart by grooves orslots. The depth of the corrugations represents a sufficient fraction ofthe wavelength of the transmitted electromagnetic energy to constitutean impedance surface which has major effects on the transmission,particularly with respect to propagated and suppressed transmissionmodes or field patterns. There are normally at least two slots perwavelength along the length of the horn, so the total number ofcorrugations in any given horn is relatively large.

Heretofore, corrugated microwave horns have generally been fabricated byconventional machining, welding and/or casting techniques. The use ofthese tech niques has made the corrugated horns costly to manufactureand has also made such manufacture a relatively slow process.Furthermore, these conventional methods of fabrication have required thehorn and the various parts thereof to have sufficient thickness to allowfor the stress of machining and/or for the flow of molten metal duringcasting. As a result, the final horn contains considerably more metalthan is required for the horn to perform its intended function, i.e.,the transmission of microwaves. Because of the well known skin effectphenomenon, the high frequency electric currents carried by such a hornflow along the surface of the horn, sothe horn can be extremely thin andstill carry the necessary current. In fact, the thicker metal is notonly unnecessary, but also is undesirable because in many cases itintroduces greater losses than are incurred with thinner metal andrequires the use of stronger and more expensive mounting and supportingstructures. 7

It is, therefore, a primary object of the present invention to providean improved construction for corrugated microwave horns which permitsthe use of metal which is substantially thinner than required by otherfabrication techniques. A more specific object of the 1 invention is toprovide such an improved construction which permits the use of metalonly a few thousandths of an inch thick.

A related object of the invention is to provide an improved constructionfor corrugated microwave horns of the foregoing type which permits thefabrication of horns which are much lighter in weight than corrugatedhorns made heretofore. In this connection, another re lated object ofthe invention is to provide such a con struction which requires lessexpensive mounting and supporting structures because of the lighterweight of the corrugated horn.

It is another object of the invention to provide such an improvedconstruction for corrugated microwave horns which permits the horns tobe fabricated in a fraction of the time required to fabricate the samehorns by conventional fabricating techniques.

5 ject of the invention is to provide such a construction which requiresonly a minimal capital investment to fabricate the horns, so that it isfeasible to fabricate a relatively small number of such horns at anygiven facility.

Still another object of the invention is to provide such an improvedcorrugated microwave horn construction which ensures accurate spacing,orientation and positioning of the various parts of the horn without theuse of any special fixtures during fabrication of the horn.

A still further object of the invention is to provide such an improvedcorrugated microwave horn construction which permits relatively longhorns to be made at a reasonable cost and a reasonable weight, so thatit becomes more feasible to use longer horns to reduce phase error.

Yet another object of the invention is to provide an improvedconstruction for tubular articles other than microwave horns that have anumber of corrugations or the like spaced along their axes, such as heatexchanger tubes and the like.

Other objects and advantages of the invention will be apparent from thefollowing detailed description together with the accompanying drawings,in which:

FIG. 6 is an exploded perspective view of a modified I embodiment of theinvention.

While the invention will be described in connection with certainpreferred embodiments, it will be understood that it is not intended tolimit the invention to those particular embodiments. On the contrary, itis intended to cover all alternatives, modifications and equivalentarrangements as may be included within the spirit and scope of theinvention as defined by the appended claims.

Tuming now to the drawings and referring first to FIG. 1, there is showna flared corrugated microwave horn having a frustoconical shell 10 witha multiplicity of parallel transverseribs or plates 11 spaced at equallongitudinal intervals along the inner surface of the shell 10. Theseplates 11 are all of equal radial width and lie in planes perpendicularto the axis of the shell 10. A flared microwave horn of the typeillustrated is normally used as a feed horn for a microwave antenna,such as a parabolic dish-type antenna. Although the horn is commonlyreferred to as a feed horn, it obviously functions as a part of theantenna system in both the sending and receiving modes. Although the artand will not be dwelled upon here. The present invention is notconcerned with a horn intended for any specific application or intendedto'meet any specific performance criteria, but rather is directed to anew construction which is generally applicable to corrugated hornsregardless of their particular shape, the number of corrugations, theslot corrugation width, the corrugation depth, etc.

In accordance with one important aspect of the present invention, thehorn shell is formed from a thin flat sheet of flexible conductive metalhaving a multiplicity of spaced slots arranged in longitudinal columnsand transverse rows, and the annular plates 11 are formed with amultiplicity of integral tabs spaced around the periphery of each platewith each tab having an aperture therethrough. Then the horn isassembled by fitting one of the tabs on each of the plates through theslots in a selected longitudinal column, inserting a wire through theapertures of those tabs to lock the slotted sheet to the annular plates,rolling the sheet around the peripheries of the plates to fit successivetabs through successive longitudinal columns of slots, and insertingwires through the apertures in successive tabs to lock the sheet tosuccessive portions of the peripheries of the annular plates. Thus, asshown most clearly in FIG. 3, the shell 10 initially comprises a thinflat sheet 12 of flexible conductive metal in the shape of an annularsegment so that when it is rolled about an axis 14 equidistant from itsnon-parallel edges, it forms the desired frustoconical horn. While thesheet 12 is still flat, a multiplicity of slots 13 are formedtherethrough in a multiplicity of longitudinal columns 13a and paralleltransverse rows 13b. The columns and rows of slots 13 are arranged sothat when the sheet 12 is rolled into the shape of the frustoconicalhorn, the'slots 13 are arranged in a series of circumferential rowslying in planes which are perpendicular to the axis of the horn andequally spaced around the circumferenc'e of the horn. Thus, in the caseof the sheet 12 illustrated for forming the frustoconical horn 10, thetransverse rows 13b lie on arcs having different radii, and both thewidth of the slots and the transverse spacing between the slots insuccessive rows gradually increases from the shorter curved edge 12a ofthe sheet 12 toward the longer curved edge 12b to maintain thelongitudinal alignment of the slots in each of the columns 13a,

For the purpose of fastening the annular plates 11 to the sheet 12 inprecisely predetermined positions relative to each other and the sheet12, while at the same time facilitating formation of the sheet 12 intothe frustoconical sheel 10, each of the plates 11 forms a multiplicityof tabs 15 around its outer periphery. The number of tabs 15 is equal tothe number of slots 13 in each transverse row 13b, taking into accountthe fact that one of the slots in each row is formed by the overlappingof two open-ended partial slots 13 formed in the two non-parallelstraight edges of the sheet 12. To ensure that each tab 15 can be fullyinserted in its corresponding slot 13 so that the sheet 12 butts againstthe periphery of the corresponding plate 11 in the spaces between thetabs, the transverse dimensions of the slots 13 are made slightly longerthan the transverse dimensions of the bases of the tabs 15.

v "In order to lock the tabbed plates 11 to the slotted mating slot 13in one of the longitudinal columns 13a, as illustrated in FIG. 3. Withthe tabs 15 all thus inserted in that one longitudinal column of slots,a wire 16 is fitted through the apertures 17 formed in each of theinserted tabs 15, extending along the outer surface of the sheet 12. Ascan be seen most clearly in FIG. 2, the apertures 17 are positioned sothat the innermost edge of the aperture 17 is flush with the outersurface of the sheet 12 when the tab 15 is fully inserted in its slot13. Also, each of the apertures 17 is dimensioned so that its diameteris only slightly larger than the outside diameter of the wire 16.Consequently, when the wire 16 is fitted through the tabs 15, theadjacent peripheral portions of the plates 11 are held tightly againstthe inside surface of the sheet 12.

After the first wire 16 is in place, the sheet 12 is gradually rolledaround the peripheries of the plates 11 with successive tabs 15 on theplates being fitted into successive longitudinal columns 13a of theslots 13 and locked thereto by means of additional wires 16. Thisoperation is repeated until the sheet 12 has been rolled around theentire circumference of the plates 11, at which point the twonon-parallel edges of the sheet 12 overlap each other to create a singlecolumn of slots meshing with the last set of tabs. Then when the lastwire 16 is inserted through the last set of tabs 15, it presses the twooverlapping edges of the sheet 12 tightly against the adjacent portionsof the plates 11 so that the final horn shell is essentially continuousaround its entire circumference, with the two overlapped edge portionsbeing held tightly against one another (see FIG. 2).

It will be appreciated that this construction permits the use of metalof minimum thickness as required by the electrical and mechanicalperformance criteria for any given microwave horn. Both the horn shell10 and the plates 11 can be made from metal that is less than 0.01 inchthick, typically 0.005 to 0.006 inch, which permits weight reductions onthe order of 20 to l as compared with similar horns made by conventionaltechniques. Because of the reduction in the amount of metal in the horn,it is much lighter in weight than conventional horns, permittingconsiderable savings in mounting and support structures. Moreover, acorrugated horn constructed in accordance with this invention can befabricated in a fraction of the time required tofabricate comparablehorns by conventional fabrieating techniques. Using this construction,it becomes feasible to manufacture relatively long horns with areasonable'weight; this is an important advantage because long horns areoften desirable for reducing phase error.

To facilitate the locking of the sheet 12 to'the multiple plates 11during the assembling operation, the slotted sheet 12 is preferably madeof a resilient material. Then as the sheet is rolled aroundthe'peripheries of the plates 11,.the resilience of the sheet 12 biasesit outwardly against the previously inserted wires 6 so as to increasethe frictional forces between the sheet 12, the wires 16 and the tabs15. These frictional forces tend to hold all the assembled elementstightlyin place so that early portions of the assembly do not come apartduring later stages of the assembling operation.

If desired, additional tabsmay be formed on the ends 'of the horn shelllll'for joining this horn section to adjacent horn se ctions, s'o that ahorn of any desired length can be made by simply interconnecting thedesired number of sections. Thus, in the illustrative embodi- UnitedStates Patent [191 McBride, Jr. et al.

[ METHOD OF MAKING LEVEL SENSOR [75] Inventors: Lyle E. McBride, Jr.,Norton;

William W. Bowman, North Easton, both of Mass; Hans A. Stoeckler,Woonsocket, R.I.; Harold A. Hanson, Pawtucket, R.l.; Joseph J. Gibola,Cumberland, R1.

[73] Assignee: Texas Instruments Incorporated,

Dallas, Tex.

[22] Filed: Aug. 21, 1974 [21] Appl. No.: 499,364

Related US. Application Data [62] Division of Ser. No. 426,872, Dec. 20,1973.

[52] US. Cl. 29/612 [51] Int. Cl H0lc 7/04 [58] Field of Search 29/610,612, 613, 614;

338/22, 25, 28, 229; 340/244 R; 73/362 AR [56] References Cited UNITEDSTATES PATENTS 2,422,925 6/1947 Rady et al 338/28 X 2,611,007 9/1952Cade et al 338/229 X Oct. 28, 1975 2,753,714 7/1956 Perkins et al.338/229 X 2,933,708 4/1960 Elliot et a1. 338/28 3,375,774 4/1968Fujimura et al.... 338/22 R X 3,832,668 8/1974 Herman 29/612 X [5 7]ABSTRACT A method of assembling a level sensor is disclosed whichincorporates the steps of soldering a first wire lead to one side of aPTC sensor pill, soldering an isolating wafer to the other side of thepill .while sandwiching a second lead therebetween, placing insulatingcovers onto the leads, inserting an insulating sleeve within a bulbousmetal can which is open at one end, and placing a solder form within thecan. The pillwafer assembly is bonded to the can by applying heat to thesolder form after which a cover member is secured to the open end of thecan hermetically sealing 1t.

7 Claims; 5 Drawing Figures

1. A method of manufacturing corrugated microwave horns and the likecomprising the steps of a. forming a plurality of thin annular plates ofconductive metal with a multiplicity of integral tabs spaced around theperiphery of each plate, each of said tabs having an aperturetherethrough, b. forming a thin flat sheet of flexible conductive metalin a shape adapted to be rolled into the form of a horn and having amultiplicity of spaced slots arranged in a multiplicity of longitudinalcolumns and transverse rows, c. fitting one of the tabs on each of saidplates through the slots in a selected longitudinal column and insertinga wire through the aperture in each of said tabs to lock the slottedmetal sheet to said plates, d. and rolling said sheet around theperipheries of said plates to fit successive tabs through successivelongitudinal columns of said slots, and inserting wires through theapertures in said tabs to lock said sheet to successive portions of theperipheries of said plates.
 2. A method as set forth in claim 1 whereinsaid plates are of circular shape with gradually increasing diametersalong the length of said sheet so as to form a flared horn.
 3. A methodas set forth in claim 1 which includes the steps of continuously joiningeach of said plates to said sheet by means of an electrically conductivemedium around the entire circumference of each plate.
 4. A method as setforth in claim 3 wherein said electrically conductive medium is solder.5. A method as set forth in claim 1 wherein said sheet and said plateshave a thickness of less than about 0.01 inch.
 6. A method as set forthin claim 1 wherein said sheet is resilient.
 7. A method as set forth inclaim 1 which includes the step of bonding said wires to the surface ofsaid sheet.
 8. A method of manufacturing a tubular article with aplurality of transverse members secured thereto, said method comprisingthe steps of a. forming a plurality of the transverse members with amultiplicity of integral tabs spaced around the periphery thereof, eachof said tabs having an aperture therethrough, b. forming a sheet offlexible resilient material in a shape adapted to be rolled into atubular form and having a multiplicity of spaced slots arranged in amultiplicity of longitudinal columns and transverse rows, c. fitting oneof the tabs on each of said transverse members through the slots in aselected longitudinal column and inserting a longitudinal locking memberthrough the aperture in each of said tabs to lock the slotted sheet tosaid transverse members, d. and fitting successive tabs throughsuccessive longitudinal columns of said slots and inserting longitudinallocking members through the apertures in said tabs to lock said sheet tosuccessive portions of the peripheries of said transverse members.
 9. Amethod of manufacturing a tubular article with a plurality of transverseplates secured to the outer surface thereof, said method comprising thesteps of a. forming a plurality of plates each forming at least oneaperture with a multiplicity of integral tabs spaced around theperiphery of the aperture, b. forming a sheet of flexible resilientmaterial with a multiplicity of spaced parallel slots arranged in amultiplicity of transverse rows, c. rolling the slotted sheet into atubular form, inserting the rolled sheet through said annular plateswhile holding it in said tubular form, and then releasing the rolledsheet so that it expands against the inner peripheries of said annularplates, d. and fitting said tabs through the slots in said sheet to lockthe annular plates to the rolled sheet.